The complexity and cost associated with power dissipation in computing systems continues to grow with increasing demands on computing performance. These systems commonly employ numerous semiconductor packages that must be coupled to sufficient power dissipation capacity. Air cooling of the packages may not be sufficient in systems incorporating highly dense physical architectures; in such instances, liquid cooling of the packages may be required.
Certain prior art techniques couple fluid (e.g., water or alcohol) directly to the semiconductor package to address thermal dissipation requirements. However, these techniques provide only a fraction of the total required thermal dissipation because most of the thermal impedance is internal to the semiconductor package, thereby dominating how thermal dissipation occurs, irrespective of coupling fluid or thermal sinks attached to the package. Accordingly, a reduction of the package's internal thermal impedance is needed in order to make significant improvement to overall thermal dissipation.
The prior art has also attempted to incorporate microchannels within the semiconductor element (or “die”) of the package, to improve cooling efficiency. Each microchannel is for example etched into the semiconductor substrate so as to provide increased cooling area to the substrate. In one example, these microchannels are formed as a series of “fins” in the substrate to assist in dissipating internally-generated heat. One difficulty with the prior art's use of microchannels is that high pressure is used to couple fluid to the die; a pressure pump forces the fluid to flow through the microchannels. This pressure pump has significant failure modes that make it risky to use within computing systems.
The prior art has also attempted to utilize “loop thermosyphon” techniques to cool the semiconductor package. Loop thermosyphon of the prior art utilizes an evaporator, such as a metal block, to thermally cool the semiconductor package by coupling cooling liquid therebetween. The package heats up to generate vapor from the liquid, and the density differences between the liquid and the vapor assists heat transfer between the evaporator and the semiconductor package. However, loop thermosyphon of the prior art also does not reduce internal thermal impedance of the semiconductor package and, therefore, it too does not dissipate enough thermally generated energy from the package.